Transcript Ciovati_Summary_of_temperature_mapping_developments

Summary of temperature mapping
developments
G. Ciovati, M. Champion
AES Cavity Meeting, JLab, August 28th 2007
Outline
• Existing capabilities
– Cornell 1-cell system, 1.5 GHz
– DESY 1- and 9-cell system, 1.3 GHz
– KEK 1-cell systems, 0.5 GHz
– Saclay 1-cell system, 1.3 GHz
– JLab 1-cell system, 1.5 GHz
• Development projects
– FNAL 1- and 9-cell system, 1.3 GHz
– LANL 9-cell system, 1.3 GHz
– JLab, 2-cell system, 1.3 GHz
Rotating vs. fixed systems
• Rotating T-map systems compared to
fixed ones have:
Reduced number of thermometers and cavity
preparation time
Longer data acquisition time
Ability to detect only “stable” losses
Reduced sensitivity in superfluid He
Existing capabilities
Cornell 1-cell 1.5 GHz
• 768 Allen-Bradley 100 W (1/8W) resistors,
distributed in 36 boards, 10 spaced.
15000
13000
R (W )
11000
9000
7000
5000
3000
1000
1.60
2.10
2.60
3.10
3.60
4.10
T (K)
Apiezon N grease used to
improve thermal contact
• Thermometer design features:
– High sensitivity at 2 K ( 15 W/mK)
– Time response 7 ms
– Linear response, between 1 mK – 1 K for power flux
between 1 mW/cm2 – 1 W/cm2
– Linear self-heating as a function of the dissipated power
in the resistor ( 1 mK for 0.2 mW)
• 2 feedthrough boxes on top of the test
stand for wiring inside/outside of cryostat
• National Instruments data acquisition
system, 140ms/scan
J. Knobloch, Ph.D. Thesis, Cornell University, 1997
DESY 1- and 9-cell system, 1.3 GHz
• The 1-cell system is a copy of the Cornell design
• The 9-cell system is rotating, 116 thermometers
distributed in 9 arms. 5 angular steps, about 1h
for complete map.
• Thermometers for rotating system:
– 100 W Allen-Bradley resistors housed in a
silver block, spring loaded contact
– The thermometer efficiency depends on
contact pressure and heat power level
Ag block
Epoxy
T. Junquera et al., Proc. of the 1995 PAC, p.1648
Q. S. Shu et al., Proc. of the 1995 PAC, p.1639 and Proc. of the 7th SRF
Workshop, p. 523
• In addition, DESY has an “equator” T-map
system with Cornell-style thermometers
• 72 thermometers divided in 24 boards, 15
spaced
Courtesy W.-D.
Moeller
KEK 1-cell systems, 0.5 GHz
• Two systems for 0.5 GHz single cells:
– fixed, 1332 resistors (51 W Allen-Bradley), 36
boards, 10 spacing, 48 s/scan
– Rotating, 25 resistors, 2 s/scan, 2-6 min/turn
T. Takahashi et al., KEK Preprint 93-102 (1993)
T. Tajima et al., KEK Preprint 92-91 (1992)
Saclay 1-cell system 1.3 GHz
• 60 thermometers (developed for DESY 9cell system) distributed on 6 arms, 60
spaced
J. Lesrel et al., Proc. of the 1998 EPAC, p.1861
M. Fouaidy et al., Proc. of the 1996 EPAC, WEP043L
JLab 1-cell system 1.5 GHz
• Based on Cornell design. 576 resistors
distributed in 36 boards, 10 spacing
• 1 feedthrough box on top of the test stand
for wiring inside/outside of cryostat
• National Instruments data acquisition
system, 1MS/s, 15ms/scan
G. Ciovati et al., JLAB Tech Note TN-05-59 (2005)
Developments
LANL 9-cell system, 1.3 GHz
• 5508 Allen-Bradley (100 W)
• 15-17 sensors per meridian cell, 10
spaced
• 36 G-10 boards cover 3 cells, 108
boards total
• 12 boards (40 coverage) will be
powered at a time to reduce the
number of cables out of the cryostat to
720
• Power switching done in the cryostat
• Expected  2s/scan
• First test expected by 09/15/07
Voltage (mV)
• The excitation voltage is
multiplexed between all
sensors, the readout
voltage occurs on the
same wire for 9 sensors
• Sensitivity at 2 K expected
to be 0.186 mV/mK
A. Canabal et al., Proc. of the 2007 PAC, p. 2406
JLab 2-cell system, 1.3 GHz
• Build a system to map the equator region of 2/9 cells of
ILC cavity identified as suspect for quench location by
TM010 pass-band measurements
• Share resources (Data acquisition, software) with the
existing single-cell system
• 320 Allen-Bradley (100 W) Cornell-style thermometers,
11 spacing, covering from weld to  3 cm down along
equator
KEK 1- and 9-cell systems 1.3 GHz
• Use RuO2 sensors
• Make shape-independent system (film
resistors)
K. Saito, private communication
FNAL 1- and 9-cell system 1.3 GHz
• Fixed systems, 960 diodes/cell, 16
sensors/board, 6 spacing
• Interchangeable boards between 1- and 9cell systems
Diode sensor
G10 board
Kapton w/
printed circuit
~1mmx1mm
sensing area
Flex shown in
compressed
state as if
contacting the
cavity
• Commercial 1N4148
–  10 mK resolution measured at 4 K
– Temperature sensitivity (dV/dT at 2 K) and
thermometer efficiency are yet to be
determined
• Standard multiplexing scheme works with
diodes, reduce no. of cables (one 64-pin
cable/cell)
• “In house” data acquisition system
• Expected  1 min/scan for 9-cell system
Cage PCB
Helium flow
holes
Card assembly, only
3 shown for clarity.
60 cards/ cell
Support system
for intial assembly
A. Mukherjee, private communication
Conclusions
• T-mapping is the most common diagnostic
tool for SRF cavities
• In the design of new systems, fixed ones
are preferred
• Systems with thousands of sensors are
being built for 9-cell cavities, multiplexing
schemes will be used to reduce cabling
• New sensors are being considered (RuO2,
diodes) to replace Allen-Bradley
(discontinued, expensive)